event - The code of the event: an EVENT_... constant.
As new event types can be introduced with new FMPP versions (even if
it happens very seldom), a progress listener implementation should
survive events that it does not understand. That is, it must not stop
with an error, but it should silently ignore the event.

src - Depending on event the source file or null.

pMode - Depending on event the proccessing mode
(Engine.PMODE_... constant) or
Engine.PMODE_NONE. Note that new processing modes may
be added as FMPP evolvers, so values that are not known be the
progress listener should be handler nicely, and never cause error.

error - The error, or null if there was no error.

param - Extra information about the event. The class and meaning of
object depends on the concrete event:

For EVENT_WARNING it is a String that
describles the reason of warning.